Search results for "electrical safety"

Interconnections criteria of grounding grids in global grounding systems

2018

A Global Grounding System is defined as the combination of local grounding systems, obtained by their interconnection, which ensures, thanks to their proximity, that no dangerous touch voltages can arise. The interconnection of grounding systems via the armors of the MV cables, between secondary substations and HV/MV stations is herein analyzed to verify the effects on touch voltages in ground-fault conditions. In particular, two main issues are discussed: 1) the transfer of dangerous voltages to secondary substations, due to ground-faults occurring at the HV/MV station; 2) the reduction in the magnitude of the ground potential rise due to ground-fault conditions at secondary substations, t…

Risk indexes for studying interconnected earthing systems inside MV networks

2006

The paper presents a risk-evaluation-based approach to the issue of interconnection between the earth electrodes of the MV/LV substations within MV networks. After a short introduction on the interconnection between earthing systems, the paper proposes four risk indexes defined starting from the safety requirements given by CENELEC HD 63 7 S1. The indexes allow one to put in evidence, in a clear way, the benefits of the interconnection in terms of reduction of risk of critical electric shock for persons and of stress on the insulation of the LV devices in the presence of single line to earth faults and double earth faults inside MV/LV substations and single line to earth faults inside HV/MV…

Multiobjective Optimal Reconfiguration of MV Networks with Different Earthing Systems

2010

The paper deals with the traditional problem of multiobjective optimal reconfiguration applied to power distribution systems considering the safety issue in the formulation. The applications are devoted to the solution of the posed problem in networks in which coexist energy sources with unearthed neutral point and resonant earthed neutral point. After a brief review of the most recent papers on optimal reconfiguration, the paper outlines the safety problem and provides a solution to the multiobjective problem using the Non dominated Sorting Genetic Algorithm II aiming at: minimal power losses operation, safety check at distribution substations and load balancing among the HV/MV transformer…

ARC FAULT DETECTION EQUIPMENT AND METHOD USING LOW FREQUENCY HARMONIC CURRENT ANALYSIS

2012

An arc fault detection circuit includes a current sensing circuit coupled to a line conductor carrying a current. The current sensing circuit operates to sense current and output data indicative of the sensed current. A processing circuit implements a frequency transform algorithm to transform the output data to frequency data in a low frequency range and with a high spectral resolution where a minimum short time observation window is concerned. The processing circuit identifies an arc fault condition on the line conductor by identifying differences in said frequency data between at least two subsequent observation windows and identifying characteristics which exceed thresholds.

Series arc faults in AC and DC electrical circuits. Characterization and detection methods

2013

This paper analyzes the problem of the arc faults in both AC and DC low voltage electrical circuits. The state-of-the-art of the arc fault detection methods is analyzed together with the UL 1699 and UL 1699B Standard requirements for protection devices against arc faults (AFCIs). An experimental characterization is carried out of the arc fault phenomenon, for both AC and DC systems, focusing the attention on series arcs. The experimental measurements are carried out on a proper test bench, which has been developed in order to reproduce significant arcing conditions, in accordance with the UL 1699 Standard requirements.

Caratterizzazione e metodi di riconoscimento degli arc faults per applicazioni in sistemi di bassa tensione

2013

Considering safety issues in minimum losses reconfiguration for MV distribution networks

2009

This paper offers a new perspective over the traditional problem of the multiobjective optimal reconfiguration of electrical distribution systems in regular working state. The issue is indeed here formulated including also safety issues. Indeed, dimensioning the earth electrodes of their own secondary substations, distribution companies take into account the probable future configurations of the network due to transformations of overhead lines into cable lines or realization of new lines. On the contrary, they do not consider that, during normal working conditions. the structure of the network can be modified for long periods as a consequence of reconfiguration manoeuvres, with differences …

Time domain symmetry parameters analysis for series arc fault detection

2022

This paper presents a feasibility study of exploiting the symmetry of some parameters for series arc fault detection in electrical circuits. The considered parameters are defined in the time domain and they are based on the current signal derivative and the evaluation of cross-correlation between subsequent observation windows. The analysis is carried out for AC systems, starting from an experimental characterization, which has been carried out in accordance with the Standard UL 1699 requirements for "unwanted tripping tests"and "operation inhibition tests"of arc fault circuit interrupters (AFCIs). The results obtained in different load conditions show that the proposed parameters can be us…